Cooperation at the Network Level

Prof. Anthony Ephremides (University of Maryland)

DATE: 2009-12-14
TIME: 11:00:00 - 12:00:00
LOCATION: RSISE Seminar Room, ground floor, building 115, cnr. North and Daley Roads, ANU

ABSTRACT:
The concept of cooperative transmissions in a wireless network evolved from the notion of the relay channel and the MIMO technology. Most of the work to date has focused on physical layer techniques (such as decode-and-forward and the like) and aimed at characterizing the source-to-destination Information-theoretic Capacity. We take a different view and exploit the possibility of relaying in a cognitive fashion. That is, we sense unused resources (time-slots and/or frequency bamds) and make opportunistic use of these resources for relaying. We consider packets and slots rather than bits and seconds and thus our approach focuses on computing throughput, rather than capacity. In fact, we consider the realistic and practical case of finite delays, and, hence, bursty source traffic; thus we focus on the "stable throughput" region that can be achieved in a network with or without relaying. We find that significant improvements can be achieved if such cooperative/cognitive methods are used. And in fact we also consider superposing on these methods the more familiar physical layer schemes (such as combining, decode-and-forward, etc) and show that we can achieve, as expected, even further gains. We then look at cooperative routing in sensor networks (a totally different concept of cooperation, again at the network level) and identify some remarkable consequences in that case.

These novel ideas and methods are the beginning of what we call "cooperation at the network level"; the potential exists that, through such cooperation, far-reaching implications may follow with regard to achievable transmission rates under bursty traffic conditions.

BIO:
Anthony Ephremides holds the Cynthia Kim Eminent Professorship Chair of Information Technology. He holds a joint appointment with the Institute for Systems Research, of which he has been a founding member, and he is a also a member of and former Co-Director of the Maryland Hybrid Networks Center (HyNET), formerly known as the Center for Hybrid and Satellite Communication Networks (CHSCN).

He received his B.S. degree in Electrical and Computer Engineering from the National Technical University of Athens, Greece, in 1967 and the M.A. and Ph.D. degrees also in Electrical Engineering from Princeton University in 1969 and 1971, respectively.

He has served in many capacities in the IEEE and other organizations, from local organization posts to President of the Information Theory Society and member of the Institute Board of Directors, including Technical Program Chair and General Chair of Major Conferences.

Research Interests:

His research interests include all aspects of Communications Systems (Information Theory, Communication Theory, Multi-user Systems, Communication Networks, Satellite Systems) with focus on Energy Efficiency and Cross-Layer Approaches to Design. He is also interested in Systems Theory, Stochastic Systems, Optimization, Signal Processing, Wireless Communications, and other related, or unrelated, subjects.

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